This invention generally relates to frequency selective surfaces. More particularly, this invention relates to systems and methods for manufacturing artificial magnetic conductors.
An artificial magnetic conductor (AMC) generally is an engineered material having a planar, electrically thin, anisotropic structure that is a high-impedance surface for electromagnetic waves. The electrically thin structure has a typical height in the range of about xcex/100 through about xcex/50, where xcex is a free space wavelength. At microwave frequencies in the range of about 300 MHz through about 3 GHz, the structure also is physically thin. A typical AMC structure is two-layered, periodic, and magnetodielectric, and is engineered to have a specific tensor permittivity and permeability behavior with frequency in each layer. The AMC properties may be limited over a frequency band or bands. Near the resonant frequency of the structure, the reflection amplitude is near unity and the reflection phase at the surface is near zero degrees. When operating as a high impedance surface, an AMC suppresses transverse electric (TE) and transverse magnetic (TM) mode surface waves over one or more frequency bands.
The high impedance surface may be used in antenna and similar applications. The antenna applications include xe2x80x9cpaste-onxe2x80x9d antennas, internal and wireless handset antennas, global positioning satellite (GPS) antennas, and the like. Other applications include suppressing surface waves, mitigating multi-path signals near the horizon, reducing the absorption of radiated power, directing the radiation pattern, and lowering the aperture size and weight.
FIG. 14 is an AMC according to the prior art. The AMC may be made using printed circuit board manufacturing and other methods know in the art to form a xe2x80x9cbed of nailsxe2x80x9d structurexe2x80x94a frequency selective surface (FSS) connected by vias to a backplane. A spacer or dielectric layer is disposed adjacent to the backplane. The spacer layer may be any material suitable for a printed circuit board substrate such as a fiber reinforced polymer, a copper laminate epoxy glass (FR4), and the like. The backplane is made from a metal such as copper. The vias are plated-through holes formed in the spacer layer and are made of a metal such as copper. The vias may be hollow or solid and are connected to the backplane. The FSS has conductive shapes printed on a substrate. The conductive shapes are made of a metal such as copper and are conductively attached to the vias. The substrate typically is much thinner than the spacer layer and may be any material suitable for a printed circuit board substrate such as polyimide.
The vias, multi-layer construction, and dissimilar layers and substrates increase manufacturing costs. The type of dielectric material also may increase the cost of AMC antennas. The dielectric material typically used as the spacer layer is relatively heavy and represents as much as 98 percent of the weight of a finished AMC. This dielectric material also may contribute significantly to the cost of thicker AMC designs. This dielectric material makes the spacer layer more rigid, so that the resulting AMC is rigid and planar. A rigid AMC may not be suitable for some applications such as those requiring a conformable (non-planar) or flexible AMC.
This invention provides an artificial magnetic conductor (AMC) system and manufacturing method. The AMC has one or more posts or post assemblies formably extending from a post plane adjacent to one or more frequency selective surfaces.
The AMC may comprise a post plane and one or more frequency selective surfaces in one embodiment. The post plane has one or more posts and one or more slots. The one or more posts formably extend from the post plane. The frequency selective surfaces have one or more conductive shapes. The posts are operatively disposed adjacent to the conductive shapes.
The AMC also may comprise one or more frequency selective surfaces and a post plane in another embodiment. The post plane has one or more post assemblies and one or more slots. The one or more post assemblies formably extend from the post plane. Each post assembly has one or more posts and one or more plates. The one or more plates are operatively disposed adjacent to the one or more frequency selective surfaces.
In a method for manufacturing an AMC, one or more posts and one or more slots are formed in a post plane. The one or more posts formably extend from the post plane. The one or more posts are operatively disposed adjacent to one or more frequency selective surfaces.
In another method for manufacturing an AMC, one or more post assemblies and one or more slots are formed in a post plane. Each post assembly has one or more posts and one or more plates. The one or more posts formably extend from the post plane. The one or more plates are operatively disposed adjacent to one or more frequency selective surfaces.
Other systems, methods, features, and advantages of the invention will be or will become apparent to one skilled in the art upon examination of the following figures and detailed description. All such additional systems, methods, features, and advantages are intended to be included within this description, within the scope of the invention, and protected by the accompanying claims.